Overview of commercial photography

[ 1]

It is the infrastructure to support social and economic development.

And then what? Circulatory system? , occupies an important position in the social and economic system. Whether the traffic problem is solved well or not directly affects the national economy.

The development of China and the improvement of people's quality of life. Now there is no shortage of traffic jams in big cities all over the world. To some extent, the traffic problem has become a restrictive factor for the stable development of economy and society? Bottleneck? However, limited land and economic constraints make it impossible for road construction to reach a relatively satisfactory mileage. Therefore, it is necessary to comprehensively use modern information and communication technologies to improve transportation efficiency and increase the capacity of the transportation network without expanding the scale of the road network. Therefore, the idea of using various high-tech systems to solve road traffic problems came into being, which is ITS(intelligenttransportsystem System).

[2-3]

Traffic control and guidance system is a popular core course in ITS research.

The key problem of realizing traffic flow guidance system is real-time and accurate traffic flow prediction, that is, how to effectively use real-time traffic data information to predict traffic conditions in the next few minutes. The results can be directly sent to Advanced Traffic Information System (ATIS) and Advanced Traffic Management System (ATMS), giving pedestrians real-time and effective information to help them better choose routes and realize roads.

Route guidance shortens travel time and reduces traffic congestion. This kind of forecast is called short-term forecast, which is in the micro sense, different from the meso and macro sense, and even the hourly, daily and monthly forecast.

The strategic forecast based on traffic planning calculated this year is fundamentally different.

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1? data acquisition

The original traffic parameter information collection methods are all non-automatic manual collection methods, including manual observation and photography. Since 1930s, the United States has developed? Voice control? Since the induction traffic signal controller, traffic detector technology has developed rapidly, especially in the past 20 years, a large number of new traffic detectors have appeared. There are many kinds of traffic detectors, mainly including coil detectors, ultrasonic detectors, magnetic induction detectors, optical radiation detectors, radar detectors, video detectors and so on. At present, there are loop coil detectors, ultrasonic detectors and video detectors widely used. 1. 1? Loop coil detector method

Loop coil detector

[6]

Appeared in the 1960 s, is

At present, traffic detectors are widely used in traffic control. The detector is a vehicle detector based on the principle of electromagnetic induction, and its sensor is a ring with a certain alternating current buried under the road.

V-shaped coil When the vehicle passes the coil or stops on the coil, the vehicle causes the change of the inductance of the coil loop, and the detector can detect this change and collect the traffic flow according to this principle. 1.2? Ultrasonic detector method

ultrasonic detector

[ 1]

By receiving the signal sent by the ultrasonic probe

The vehicle is detected by ultrasonic waves reflected from the vehicle. The working principle of ultrasonic flaw detector can be divided into two types: propagation time difference method and Doppler method.

Propagation time difference method, the probe of ultrasonic detector emits ultrasonic waves to the road surface, and then receives its reflected waves. When there is a vehicle, the ultrasonic wave will be reflected by the vehicle and return in advance. Doppler method, the ultrasonic probe emits ultrasonic waves into space and receives signals at the same time. If there is a moving object, the received reflected wave signal will have Doppler effect.